On Fri, May 3, 2019 at 12:30 PM Stefano Garzarella <sgarz...@redhat.com> wrote: > > RBD APIs don't allow us to write more than the size set with > rbd_create() or rbd_resize(). > In order to support growing images (eg. qcow2), we resize the > image before write operations that exceed the current size. > > Signed-off-by: Stefano Garzarella <sgarz...@redhat.com> > --- > v2: > - use bs->total_sectors instead of adding a new field [Kevin] > - resize the image only during write operation [Kevin] > for read operation, the bdrv_aligned_preadv() already handles reads > that exceed the length returned by bdrv_getlength(), so IMHO we can > avoid to handle it in the rbd driver > --- > block/rbd.c | 14 +++++++++++++- > 1 file changed, 13 insertions(+), 1 deletion(-) > > diff --git a/block/rbd.c b/block/rbd.c > index 0c549c9935..613e8f4982 100644 > --- a/block/rbd.c > +++ b/block/rbd.c > @@ -934,13 +934,25 @@ static BlockAIOCB *rbd_start_aio(BlockDriverState *bs, > } > > switch (cmd) { > - case RBD_AIO_WRITE: > + case RBD_AIO_WRITE: { > + /* > + * RBD APIs don't allow us to write more than actual size, so in > order > + * to support growing images, we resize the image before write > + * operations that exceed the current size. > + */ > + if (off + size > bs->total_sectors * BDRV_SECTOR_SIZE) {
When will "bs->total_sectors" be refreshed to represent the correct current size? You wouldn't want a future write whose extent was greater than the original image size but less then a previous IO that expanded the image to attempt to shrink the image. > + r = rbd_resize(s->image, off + size); > + if (r < 0) { > + goto failed_completion; > + } > + } > #ifdef LIBRBD_SUPPORTS_IOVEC > r = rbd_aio_writev(s->image, qiov->iov, qiov->niov, off, c); > #else > r = rbd_aio_write(s->image, off, size, rcb->buf, c); > #endif > break; > + } > case RBD_AIO_READ: > #ifdef LIBRBD_SUPPORTS_IOVEC > r = rbd_aio_readv(s->image, qiov->iov, qiov->niov, off, c); > -- > 2.20.1 > > -- Jason